Food storage containers

ABSTRACT

A food container having an injection moulded polypropylene body with an open end around which extends a circumferential flange to which a metal lid having a frusto-conical annular wall is attachable. The walls of the container are tapered in thickness near the open end to accommodate the outwardly flaring frustoconical wall so that the wall can provide suitable support for the container wall during a seaming operation where the lid is seamed to the flange by means of a conventional tin can seaming machine.

United States Patent Nughes 1 Jan. 9, 1973 [54] FOOD STORAGE CONTAINERSFOREIGN PATENTS OR APPLICATIONS [75] Inventor: GiovanniNuglies','MiI5nIIial 563,775 '9/1958 Canada ..220 42 [22] Filed: W July21, 197 1 V I I Primary Examiner-Joseph R. Leclair AssistantExaminer-James R. Garrett [21] Appl Attorney--Richatd C. Sughrue et al.30] raragsapmrcaaanFriorrtymia" [57] ABSTRACT Aug. 11,1970 Italy..69772A/70 A food container having an injection moulded [52]U.S.i2l..'.'.' I....'.III...'. ....IIQ....I....Lii0/67 P yp py y t all Pend around which [51] Int. Cl. ..B65d 7/42 extends a circumferentialflange to which a metal lid [58] Fi ld f S h 220/67 42 B, 42 C; 150/,5having a frusto-conical annular wall is attachable. The

' walls of the container are tapered in thickness near [56] Referen esCi d the open end to accommodate the outwardly flaring frusto-conicalwall so that the wall can provide suita- UNITED STATES PATENTS blesupport for the container wall during a seaming 2 382 378 3 Bloedom220/67) operation where the lid is seamed to the flange by 2:8l6z58912/1957 Tupperum I I l I "150/5 means ofa conventional tin can seamingmachine. 3,073,478 Ill 963 Henchert ..220/67 3,341,059 9/1967 Schild etal.... ..220/67 6 Claims 6 Drawing Fgms 3,524,568 8/1970 Nughes ..220/673,543,963 12/1970 Hcisler et al. ..220/67 10 11. L. Rf I \\\\q F I 12 r16A 10A 16B A PATENTEUJMI 9 197a SHEET 1 [IF 4 Eiql I PRIOR ART INVENTOR5/0 VA N/Y/ Noah/6 51 4M 72 /4012? M 1 BY 2 I a a #L ATTORNEYS seam andthe lid seam meet.

The present invention relates to food storage containers having asubstantially rigid polypropylene body of low yieldability. v

The body of such containers is conveniently injection moulded and has acircular cylindrical shape similar'to that conventional tin can"although a variety of other suitable shapes may be employed. Asdescribed in my earlier U.S. Pat. No. 3,5 24,568 the body of thecontainer is formed with an outwardly directed circumferential flange atthe open end and a metal lid can be seamed to the flange of the body bymeans of a conventional double hook seam. In this way it is possible touse the novel polypropylene can body in conjunction with conventionalmetal lids and to join the body and the lid tin plate, the angle betweenthe shoulder forming wall together by means of a conventional seam on aconventional' seaming machine operating on the so-called seam spinningprinciple. For this purpose the metal lids are formed with a peripheralflange parallel to the general plane of the lid axially displaced fromthis plane by a smallamount and joined to the main disc of the lid byanaxially extending wall.

Storage containers of this type are particularly suited for themanufacturing of food produce in view of various problems such assterilization, longitudinal seaming, transference of metallic taste andsusceptibility to acid and hydrogen sulphide attack, encountered withthe use of metal cans which are explained in greaterdetail in U.S. Pat.No. 3,524,568. Many of these problems are overcome, or at leastminimized by the use of the polypropylene containerbody; for example, apolypropylene body can be injected moulded and thus does not have alongitudinal side seam as do conventional metal cans. There is thus norisk of the side seam weakening and no weak The importance of thedetailed configuration of the outwardly directed circumferentialflangefor satisfactory seaming to a metal lid is also discussed in U.S. Pat.No. 3,524,568. It has previously been considered essential for thecircumferential flange to be formed with a progressively tapering crosssection reducing from the region where theflange meets the'body of thecam to a minimum at the periphery of the flange in order-to ensure asatisfactory seam with the metal lid.

It has now been found however, that, irrespective of any tapering of theflange, the seaming operation is stronglyinfluenced by the relativeconfiguration of the can and the lid in the region of thewall of thelid. In

points where the side I particular, it has been found that the supportwhich the v wall of the lid is able to offer the body of the container,in the region of the opening, during the seaming process greatly affectsthe efficacy of the seaming process. It has also been found that, oncethe problems connected with this phenomena are overcome, the thicknessof the flange can be constant without deleteriously affecting theefficacy of the seaming process.

Considering, for example, a cylindrical container (of the type of thecommon tin can), it is known that the small axially extending wallportion of the lid which forms the above mentioned wall is never trulycylindrical, but has a slightly conical shape due to the conditionsunder which the lid is formed. This conical shape varies from case tocase; for example, in lids made of and the longitudinal axis of the lid(the cone angle) is typically between about 5 and about 6"30', while inlids of aluminum the cone angle varies in the range from about 330 toabout 430. It will be seen that the angles under consideration are verysmall and, until now, they have never been given particular importancein regard to the seaming process, particularly because the variation ofthe diameter of the shoulder wall from the narrowest part to the widestpart due to such a small cone angle appeared to be insignificant.

It has now been found, however, that polypropylene containers asdescribed in the patent mentioned above are very sensitive to this smalldeviation from a true cylindrical shape. In particular it has been foundthat as alid is pressed into the opening of a polypropylene containerthe taper of the lid wall causes a radially outward pressure on thecontainer walls which has a maximum value at the end of the wall wherethe outwardly turned flange is situated. As a result of this pressure,and as a result of the difference between the taper of the lid wall andthe-shapeof the container wall there is a lack of radial support fromthe inside of the container wall during the seaming operation, and thisdeleteriously affects the efficacy of the seaming operation. To avoidthis defeet the diameter of the lid wall could be increased slightly sothat the lid would enlarge the container wall when pressed into theopening of the container body. However, it is possible, in-this case,for the circumferential flange to .warp and therefore to miss the hookformed by the flange during the seaming operation thereby forming anincomplete seal between the body and the lid.

According to the present invention a container for food comprises apolypropylene body of low yieldability having an open end with acircumferential flange and a metal lid seamed to the. circumferentialflange, in which the lid has a frusto conical annular wall and thecontainer wall is tapered in thickness toward the said open end, thelength of the tapered portion being at least equal to the depth of thesaid frusto-conical wall.

This tapered portion of the container wall extends to the arcuatetransition region between the container wall and the circumferentialflange, beginning from which the thickness of the flange may be constantor, if desired, may still taper towards the outer edge of the flange inthe known way. Preferably the container wall is bevelled internally, thebevelled. portion being at an angle to the axis of the can which is atleast equal to the angle of the wall of the lid. Typically, the angle ofbevel is in the range from about 3 to about 10, depending on the angleof taper of the wall of the lid;

In one embodiment of this invention, the angle of bevel of the inside ofthe container wall is slightly greater than the angle of taper of thewall of the lid so that the pressure between the lid wall and thecontainer wall is greatest at the region of contact between the lid andthe wall remote from the flange. The lid wall thus deforms the containerwall as the lid is pressed into the opening, and this deformation issuch asto ensure intimate contact between the flange of the lid and thecircumferential flange of the container.

Various embodiments of the present invention will now bemoreparticularly described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 is a partial axial section of part of a wall of a known type ofpolypropylene container showing a lid in position but before seaming;

FIG. 2 is a partial axial section of a part of a wall of a known type ofpolypropylene container in the same position as FIG. 1 but showing a lidof larger diameter in position;

FIG. 3 is a partial axial section of part of a wall of one embodiment ofthe invention;

FIG. 4 is a partial axial section of part of a wall of a secondembodiment of the invention;

FIG. 5 is a partial axial section-of part of the wall of a thirdembodiment showing a lid immediately before it is pressed into theopening; and

FIG. 6 is a partial axial section of the embodiment of FIG. 5 showing alid after it has been pressed into position but before a circumferentialseam has been formed.

Referring now to FIGS. 1 and 2 these illustrate the disadvantagesdiscussed above, of a lack of radial support for a container wall 16 bya wall 12 of a lid 10- pressed onto a container 14. As will be seen inFIG. 1, due to the slight taper of the wall 12 (shown exagerated inFIG. 1) there is a gap 18 between the wall 16 and the wall 12 extendingthe length of the wall 12 with the exception of the end where it meetsthe flange. The presence of this gap means that the wall 12 cannotprovide the required support to hold the wall 16 rigidly during theseaming operation and this results in frequent failures and difficultiesin the seaming operation. The proposed attempt to provide suitableradial support by increasing the diameter of the lid 10, however,frequently leads to buckling of the circumferential flange 20 as shownin FIG. 2. This in turn results in the flange 10B of the lid 10 failingto make a satisfactory seal with the buckled portion of the flange.

In the embodiment illustrated in FIG. 3 the wall 16 of the containerbody 14 is progressively reduced in thickness from the inside, from alevel 22 lower-than that of the central disc 10A of the lid 10 when thelid 10 is in position. This reduction in thickness is effectively in theform of a bevel the angle of which is substantially the same as theangle of the wall 12 so that the wall fits snugly into thefrusto-conical opening formed by the bevel 16A. Thus, during the seamingoperation, the bevelled portion 16A of the wall 16 is supported radiallyby the wall 12.

The embodiment illustrated in FIG. 4 is similar to that of FIG. 3,except that the frustoconical opening formed-by the bevel 16A has a step168 at the level of the central disc 10A of the lid l0. This arrangementhas the advantage that when the lid 10 is removed by a conventional canopener which cuts or shears the lid at the line 24 the sharp edge thusproduced will not project dangerously from the inside surface of thecontainer.

in the embodiment illustrated in FIG. 5, the angle X of the bevel 16A isslightly greater than the angle X of the wall 12 of the lid (as seen incross section). For example, the angle X could be 10 if the angle X were6. The diameter D of the upper end of the wall 12 adjacent the lidflange 10C is equal to the diameter of the corresponding part of theopening 16A of the container body 14. Consequently, when the lid 10 ispressed onto the container body 14 the bevelled region 16A of thecontainer wall 16 is deformed by the wall 12 of the lid 10 as shown inFIG. 6. In this case the greatest pressure between the wall 12 and thecontainer wall 16 occurs at the level of the central disc 10A of thelid. As a consequence, there is a progressive deformation of the wall 16of the container body 14 in the direction indicated by the arrow M inFIG. 6. In this case the container wall in the bevelled region 16A isfirmly radially supported by the wall 12 due to the fact that there is apressure between the wall 12 and the wall 16. Moreover, the expansionindicated by the arrow M causes the flange 20 to be pressed against thecorresponding part of the flange 10C of the lid so that the flange 20 isin positive engagement with this flange, and the hooked part 108 of theflange 10C readily engages the flange 20 during seaming.

It will be appreciated that the above described invention can be appliednot only to containers with circular cross section, which are the mostcommon type of container, but also to containers of any other shapewhich allow the manufacture of a double hook seam, for exampleelliptical or rectangular with rounded angles (of the type frequentlyused for corned beef) and other cross sectional shapes may be used. Insuch cases the frusto-conical opening will not be that of a circularcone but of some other base shape. The references in this specificationto the cone angle of such shapes will be understood to refer to theangle of inclination of the planes of the figure with respect to theaxis of the con tainer. Moreover, it should be borne in mind thatnominally cylindrical containers made by injection moulding are, inpractice, slightly conical to make it possible to remove them from themould; therefore, the reference line 30 in FIGS. 3, 4 and 5 should beconsidered as parallel to the wall of the container (in longitudinalsection) rather than parallel to the axis of the container.

Furthermore, it will be appreciated that the thickness of the containerwall depends on the size of the container. For example in FIGS. 3-6,with cylindrical containers with a diameter of 8-12 cm, the thickness ofthe part 16 may typically be about 1.5 to about 2mm and.

decreases to about 0.4 mm at the flange 20. The maximum value of thedeformation of the container wall 16 illustrated in FIG. 6 ispractically very small considering that the height H ofthe shoulder 12of the lid 10 (FIG. 5) amounts generally to 2.5-6 mm and that thedifference between the angles X and X is not more than about 7.

What I claim is: l. A container for food, said container comprising apolypropylene body of low yieldability having a side wall defining anopen end,

a circumferential flange on said body at said open end,

an outwardly flaring frusto-conical annular wall on said lid,

said side wall having a circumferential portion tapered in thicknesstowards said open end adjacent said open end, said tapered portion ofsaid container wall is formed by an internal bevel on the'inner surfaceof the container wall, the length of said tapered portion axially of thecontainer being at least equal to the depth of said frustoconical wallon said lid.

2. The container of claim 1 wherein the angle of said bevel, withrespect to the longitudinal axis of said container being at least equalto the cone angle of said wall jacent to and co-operating with said wallon said lid.

6. The container of claim 1 wherein the angle of said tapered portion ofsaid container wall is greater than thecone angle of said frusto-conicalannular wall on said lid, said lid deforming said tapered portion ofsaid container wall, when in position in said opening, by an amountincreasing progressively away from said open end for the depth of saidlid wall.

UNITED STATES PATENT OFFICE CERTIFICATE GE CORRECTION Patent No. 3, 709;399 Dated January 9, 1973 In Giovanni Nughes It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

In The Heading:

The Assignees Name was omitted. Should read:

-Assignee: Star Stabilimento Alimentare S. p.A. Milan, Italy-- Signedand sealed this 13th day of November 1973.

(SEAL) Attest:

EDWARD M.FLETCfiER,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents FORM PO-1050 (10-69) USCOMM-DC 60376-1 69 w u,s.GOVERNMENT PRINTlNG OFFICE: I969 o-qss-aaa,

1. A container for food, said container comprising a polypropylene bodyof low yieldability having a side wall defining an open end, acircumferential flange on said body at said open end, an outwardlyflaring frusto-conical annular wall on said lid, said side wall having acircumferential portion tapered in thickness towards said open endadjacent said open end, said tapered portion of said container wall isformed by an internal bevel on the inner surface of the container wall,the length of said tapered portion axially of the container being atleast equal to the depth of said frusto-conical wall on said lid.
 2. Thecontainer of claim 1 wherein the angle of said bevel, with respect tothe longitudinal axis of said container being at least equal to the coneangle of said wall on said lid.
 3. The container of claim 2 wherein theangle of said bevelled portion lies in the range 3* to 10*.
 4. Thecontainer of claim 1 wherein the axial length of said tapered portion isgreater than the depth of said lid.
 5. The container of claim 1 whereinsaid tapered portion of said container wall includes an annular stepadjacent to and co-operating with said wall on said lid.
 6. Thecontainer of claim 1 wherein the angle of said tapered portion of saidcontainer wall is greater than the cone angle of said frusto-conicalannular wall on said lid, said lid deforming said tapered portion ofsaid container wall, when in position in said opening, by an amountincreasing progressively away from said open end for the depth of saidlid wall.